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Is it safe, with respect to the data on a USB drive, to power it down while the computer is suspended, and then power it back up before resuming? E.G. are buffers on the USB drive flushed as part of the suspend procedure? Are there likely to be any other unfortunate side effects?

Specifically under Maverick "10.10" Meerkat, with an IDE (PATA) drive, but of course it would be useful to get info on a variety of setups.

Note: by "suspend" I mean the S3, "mem" sleep state. However, answers pertaining to hibernation (S4) would also be helpful.

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related: askubuntu.com/questions/20266/… –  intuited Jan 6 '11 at 7:53

2 Answers 2

when you power down the system it automatically gets ejected. and inserting it during powerup doesn't cause any damage..

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I have done this with my system using powertop, no side effects. In fact most usb devices are powered down during suspend by default, and since that is normal, shouldn't cause problems for you in this case.

EDIT: in a simple sense, your drive will be fine on suspend. The problem will occur if you take it out and use it in another system. It also depends on the level sleep your system is doing (S1, 2, 3 etc).

NB: As noted in the comment below, this will not be true if you remove the drive and use it before you resume.

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If not flush, data will be damaged. Since you may insert your drive in another computer and do some writing, then return and resume, and fs headers will be inconsistent. –  Extender Dec 1 '10 at 5:13
    
Are you sure that suspend does not flush disk buffers? That seems an unsafe default to me. What if you run out of battery while suspended? While some shutdown-with-unflushed-disk scenarios are unavoidable, it seems that this one is and not taking advantage of the opportunity is an unnecessary risk. Do you have a reference documenting what the system does on suspend? –  Michael Ekstrand Dec 1 '10 at 17:54
    
How is powertop related? –  intuited Dec 2 '10 at 0:37
    
That link is quite helpful, +1 for that. Though it doesn't really get into the specifics of what will be done to a USB drive during the suspend process. BTW by "suspend" I mean S3, though info on S4 (what I would call "hibernate") is also helpful. From what you've said so far I'm left thinking that buffers are in fact flushed, and wondering what other aspects of the drive's state could be muddied by use with another machine. –  intuited Dec 2 '10 at 0:52
    
powertop implements some power saving features, like autosuspending usb devices, and in my experience it usually means the drive/usb device is put into a "power saving mode". I may remove it though to avoid confusion (Since I updated my answer). –  RolandiXor Dec 2 '10 at 4:14

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